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Chinook Salmon (chinook + salmon)
Terms modified by Chinook Salmon Selected AbstractsThe Interplay between Climate Variability and Density Dependence in the Population Viability of Chinook SalmonCONSERVATION BIOLOGY, Issue 1 2006RICHARD W. ZABEL análisis de viabilidad poblacional; especies en peligro; Oncorhynchus tshawytscha Abstract:,The viability of populations is influenced by driving forces such as density dependence and climate variability, but most population viability analyses (PVAs) ignore these factors because of data limitations. Additionally, simplified PVAs produce limited measures of population viability such as annual population growth rate (,) or extinction risk. Here we developed a "mechanistic" PVA of threatened Chinook salmon (Oncorhynchus tshawytscha) in which, based on 40 years of detailed data, we related freshwater recruitment of juveniles to density of spawners, and third-year survival in the ocean to monthly indices of broad-scale ocean and climate conditions. Including climate variability in the model produced important effects: estimated population viability was very sensitive to assumptions of future climate conditions and the autocorrelation contained in the climate signal increased mean population abundance while increasing probability of quasi extinction. Because of the presence of density dependence in the model, however, we could not distinguish among alternative climate scenarios through mean , values, emphasizing the importance of considering multiple measures to elucidate population viability. Our sensitivity analyses demonstrated that the importance of particular parameters varied across models and depended on which viability measure was the response variable. The density-dependent parameter associated with freshwater recruitment was consistently the most important, regardless of viability measure, suggesting that increasing juvenile carrying capacity is important for recovery. Resumen:,La viabilidad de poblaciones esta influida por fuerzas conductoras como la denso dependencia y la variabilidad climática, pero la mayoría de los análisis de viabilidad poblacional (AVP) ignoran estos factores debido a limitaciones en la disponibilidad de datos. Adicionalmente, los AVP simplificados producen medidas limitadas de la viabilidad poblacional tales como la tasa anual de crecimiento poblacional (,) o el riesgo de extinción. Aquí desarrollamos un AVP "mecanicista" de Oncorhynchus tshawytscha en el que, con base en datos detallados de 40 años, relacionamos el reclutamiento de juveniles en agua dulce con la densidad de reproductores, y la supervivencia en el océano al tercer año con índices mensuales de condiciones oceánicas y climáticas a amplia escala. La inclusión de la variabilidad climática en el modelo produjo efectos importantes: la viabilidad poblacional estimada fue muy sensible a las suposiciones de condiciones climáticas futuras y la autocorrelación contenida en la señal climática aumentó la abundancia poblacional promedio al mismo tiempo que incrementó la probabilidad de cuasi extinción. Sin embargo, debido a la presencia de denso densidad en el modelo no pudimos distinguir entre escenarios climáticos alternativos a través de los valores promedio de ,, lo que enfatiza la importancia de considerar medidas múltiples para dilucidar la viabilidad poblacional. Nuestros análisis de sensibilidad demostraron que la importancia de parámetros particulares varió en los modelos y dependió de la medida de viabilidad utilizada como variable de respuesta. El parámetro de denso dependencia asociada con el reclutamiento en agua dulce consistentemente fue el más importante, independientemente de la medida de viabilidad, lo que sugiere que el incremento en la capacidad de carga de juveniles es importante para la recuperación. [source] Optimum Postmortem Chilled Storage Temperature for Summer and Winter Acclimated, Rested, Chinook Salmon (Oncorhynchus tshawytscha) White MuscleJOURNAL OF FOOD SCIENCE, Issue 5 2000A.R. Jerrett ABSTRACT Chemical anaesthesia (AQUI-STM) was used to harvest 2 groups of tank-reared chinook salmon (Oncorhynchus tshawytscha), naturally acclimated to summer (18.8 °C) and winter (10.7 and 12.4 °C) temperatures, in a "rested"state. Carcasses were stored in 35% seawater at temperatures between approximately 2 and 19 °C to investigate the effects of acclimation and storage temperature on the postmortem metabolic rate of rested epaxial white muscle tissue. Muscle pH, [lactate], and adenosine triphosphate/inosine monophosphate measurements made 20 h postharvest indicated that winter acclimated fish were 2.2 times more sensitive to temperature than summer fish. A 3rd group of winter acclimated fish, stored between ,1.2 and 6 °C, indicated that significant cold injury only occurred on freezing. [source] Pacific Salmon Extinctions: Quantifying Lost and Remaining DiversityCONSERVATION BIOLOGY, Issue 4 2007RICHARD G. GUSTAFSON biodiversidad; diversidad de salmones; extinción de poblaciones; historia de vida de salmones Abstract:,Widespread population extirpations and the consequent loss of ecological, genetic, and life-history diversity can lead to extinction of evolutionarily significant units (ESUs) and species. We attempted to systematically enumerate extinct Pacific salmon populations and characterize lost ecological, life history, and genetic diversity types among six species of Pacific salmon (Chinook [Oncorhynchus tshawytscha], sockeye [O. nerka], coho [O. kisutch], chum [O. keta], and pink salmon [O. gorbuscha] and steelhead trout [O. mykiss]) from the western contiguous United States. We estimated that, collectively, 29% of nearly 1400 historical populations of these six species have been lost from the Pacific Northwest and California since Euro-American contact. Across all species there was a highly significant difference in the proportion of population extinctions between coastal (0.14 extinct) and interior (0.55 extinct) regions. Sockeye salmon (which typically rely on lacustrine habitats for rearing) and stream-maturing Chinook salmon (which stay in freshwater for many months prior to spawning) had significantly higher proportional population losses than other species and maturation types. Aggregate losses of major ecological, life-history, and genetic biodiversity components across all species were estimated at 33%, 15%, and 27%, respectively. Collectively, we believe these population extirpations represent a loss of between 16% and 30% of all historical ESUs in the study area. On the other hand, over two-thirds of historical Pacific salmon populations in this area persist, and considerable diversity remains at all scales. Because over one-third of the remaining populations belong to threatened or endangered species listed under the U.S. Endangered Species Act, it is apparent that a critical juncture has been reached in efforts to preserve what remains of Pacific salmon diversity. It is also evident that persistence of existing, and evolution of future, diversity will depend on the ability of Pacific salmon to adapt to anthropogenically altered habitats. Resumen:,Las extirpaciones generalizadas de poblaciones y la consecuente pérdida de diversidad ecológica, genética y de historia natural puede llevar a la extinción de unidades evolutivamente significativas (UES) y especies. Intentamos enumerar sistemáticamente a las poblaciones extintas de salmón del Pacífico y caracterizar a los tipos de diversidad ecológica, de historia natural y genética de seis especies de salmón del Pacífico Oncorhynchus tshawytscha, O. nerka, O. kisutch, O. keta, y O. gorbuscha; y trucha O. mykiss en el occidente de Estados Unidos. Estimamos que, colectivamente, se ha perdido a 29% de casi 1400 poblaciones históricas de estas seis especies en el Pacífico Noroeste y California desde la colonización europea. En todas las especies hubo una diferencia altamente significativa en la proporción de extinción de poblaciones entre regiones costeras (0.14 extintas) e interiores (0.55 extintas). O. nerka (que típicamente cría en hábitats lacustres) y O. tshawytscha (que permanece en agua dulce por muchos meses antes del desove) tuvieron pérdidas poblacionales significativamente mayores que las otras especies y tipos de maduración. Se estimó que las pérdidas agregadas de componentes mayores de la biodiversidad ecológica, de historia natural y genética en todas las especies fueron de 33%, 15% y 27%, respectivamente. Colectivamente, consideramos que estas extirpaciones de poblaciones representan una pérdida entre 16% y 30% de todas las UES históricas en el área de estudio. Por otro lado, más de dos tercios de las poblaciones históricas de salmón del Pacífico persisten en esta área, y aun hay considerable diversidad en todas las escalas. Debido a que más de un tercio de las poblaciones restantes pertenecen a especies enlistadas como amenazadas o en peligro en el Acta de Especies en Peligro de E. U. A., es evidente que se ha llegado a una disyuntiva crítica en los esfuerzos para preservar lo que queda de la diversidad de salmón del Pacífico. También es evidente que la persistencia de la diversidad existente, y su futura evolución, dependerá de la habilidad del salmón del Pacífico para adaptarse a hábitats alterados antropogénicamente. [source] The Interplay between Climate Variability and Density Dependence in the Population Viability of Chinook SalmonCONSERVATION BIOLOGY, Issue 1 2006RICHARD W. ZABEL análisis de viabilidad poblacional; especies en peligro; Oncorhynchus tshawytscha Abstract:,The viability of populations is influenced by driving forces such as density dependence and climate variability, but most population viability analyses (PVAs) ignore these factors because of data limitations. Additionally, simplified PVAs produce limited measures of population viability such as annual population growth rate (,) or extinction risk. Here we developed a "mechanistic" PVA of threatened Chinook salmon (Oncorhynchus tshawytscha) in which, based on 40 years of detailed data, we related freshwater recruitment of juveniles to density of spawners, and third-year survival in the ocean to monthly indices of broad-scale ocean and climate conditions. Including climate variability in the model produced important effects: estimated population viability was very sensitive to assumptions of future climate conditions and the autocorrelation contained in the climate signal increased mean population abundance while increasing probability of quasi extinction. Because of the presence of density dependence in the model, however, we could not distinguish among alternative climate scenarios through mean , values, emphasizing the importance of considering multiple measures to elucidate population viability. Our sensitivity analyses demonstrated that the importance of particular parameters varied across models and depended on which viability measure was the response variable. The density-dependent parameter associated with freshwater recruitment was consistently the most important, regardless of viability measure, suggesting that increasing juvenile carrying capacity is important for recovery. Resumen:,La viabilidad de poblaciones esta influida por fuerzas conductoras como la denso dependencia y la variabilidad climática, pero la mayoría de los análisis de viabilidad poblacional (AVP) ignoran estos factores debido a limitaciones en la disponibilidad de datos. Adicionalmente, los AVP simplificados producen medidas limitadas de la viabilidad poblacional tales como la tasa anual de crecimiento poblacional (,) o el riesgo de extinción. Aquí desarrollamos un AVP "mecanicista" de Oncorhynchus tshawytscha en el que, con base en datos detallados de 40 años, relacionamos el reclutamiento de juveniles en agua dulce con la densidad de reproductores, y la supervivencia en el océano al tercer año con índices mensuales de condiciones oceánicas y climáticas a amplia escala. La inclusión de la variabilidad climática en el modelo produjo efectos importantes: la viabilidad poblacional estimada fue muy sensible a las suposiciones de condiciones climáticas futuras y la autocorrelación contenida en la señal climática aumentó la abundancia poblacional promedio al mismo tiempo que incrementó la probabilidad de cuasi extinción. Sin embargo, debido a la presencia de denso densidad en el modelo no pudimos distinguir entre escenarios climáticos alternativos a través de los valores promedio de ,, lo que enfatiza la importancia de considerar medidas múltiples para dilucidar la viabilidad poblacional. Nuestros análisis de sensibilidad demostraron que la importancia de parámetros particulares varió en los modelos y dependió de la medida de viabilidad utilizada como variable de respuesta. El parámetro de denso dependencia asociada con el reclutamiento en agua dulce consistentemente fue el más importante, independientemente de la medida de viabilidad, lo que sugiere que el incremento en la capacidad de carga de juveniles es importante para la recuperación. [source] Relationship between biotic ligand model-based water quality criteria and avoidance and olfactory responses to copper by fishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2010Joseph S. Meyer Abstract The U.S. Environmental Protection Agency's (U.S. EPA) water quality criteria for Cu were tested to determine whether they protect fish against neurophysiological impairment. From published studies with rainbow trout (Oncorhynchus mykiss), Chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), and fathead minnows (Pimephales promelas), 20% inhibition concentrations (IC20s) were calculated for avoidance of Cu-containing water and for impairment of electroencephalogram (EEG) and electro-olfactogram (EOG) responses to natural odorants in Cu-containing water. Additionally, a Cu-olfactory biotic ligand model (BLM) that fits the coho salmon EOG data was parameterized by changing the sensitivity parameter in the ionoregulatory-based BLM. The IC20s calculated from reported Cu avoidance, EEG, and EOG data and IC20s predicted by the olfactory BLM were compared with acute and chronic Cu criteria calculated using U.S. EPA's BLM 2007 or hardness-adjustment equations. The BLM-based chronic criteria were protective in all 16 exposure water,species combinations used in avoidance and olfaction experiments. Additionally, the BLM-based acute criteria were protective in all 11 exposure water,species combinations in which comparisons could be made with olfactory BLM-predicted IC20s but not in two of the 16 exposure water,species combinations in which comparisons could be made with the reported IC20s (which were ,8% lower than but did not differ significantly from the BLM-based acute criteria; p,>,0.05). In effect, the olfactory BLM factored out the relatively high variability in the reported IC20s. It is concluded that the U.S. EPA's BLM-based water quality criteria for Cu protect against these types of neurophysiological impairment in the six species,endpoint combinations analyzed in this paper. However, the U.S. EPA's hardness-based criteria for Cu sometimes were considerably underprotective and sometimes were much less protective than the BLM-based criteria. Environ. Toxicol. Chem. 2010;29:2096,2103. © 2010 SETAC [source] ORIGINAL ARTICLE: Potential for anthropogenic disturbances to influence evolutionary change in the life history of a threatened salmonidEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2008John G. Williams Abstract Although evolutionary change within most species is thought to occur slowly, recent studies have identified cases where evolutionary change has apparently occurred over a few generations. Anthropogenically altered environments appear particularly open to rapid evolutionary change over comparatively short time scales. Here, we consider a Pacific salmon population that may have experienced life-history evolution, in response to habitat alteration, within a few generations. Historically, juvenile fall Chinook salmon (Oncorhynchus tshawytscha) from the Snake River migrated as subyearlings to the ocean. With changed riverine conditions that resulted from hydropower dam construction, some juveniles now migrate as yearlings, but more interestingly, the yearling migration tactic has made a large contribution to adult returns over the last decade. Optimal life-history models suggest that yearling juvenile migrants currently have a higher fitness than subyearling migrants. Although phenotypic plasticity likely accounts for some of the change in migration tactics, we suggest that evolution also plays a significant role. Evolutionary change prompted by anthropogenic alterations to the environment has general implications for the recovery of endangered species. The case study we present herein illustrates the importance of integrating evolutionary considerations into conservation planning for species at risk. [source] ORIGINAL ARTICLE: Big dams and salmon evolution: changes in thermal regimes and their potential evolutionary consequencesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2008Michael J. Angilletta Jr Abstract Dams designed for hydropower and other purposes alter the environments of many economically important fishes, including Chinook salmon (Oncorhynchus tshawytscha). We estimated that dams on the Rogue River, the Willamette River, the Cowlitz River, and Fall Creek decreased water temperatures during summer and increased water temperatures during fall and winter. These thermal changes undoubtedly impact the behavior, physiology, and life histories of Chinook salmon. For example, relatively high temperatures during the fall and winter should speed growth and development, leading to early emergence of fry. Evolutionary theory provides tools to predict selective pressures and genetic responses caused by this environmental warming. Here, we illustrate this point by conducting a sensitivity analysis of the fitness consequences of thermal changes caused by dams, mediated by the thermal sensitivity of embryonic development. Based on our model, we predict Chinook salmon likely suffered a decrease in mean fitness after the construction of a dam in the Rogue River. Nevertheless, these demographic impacts might have resulted in strong selection for compensatory strategies, such as delayed spawning by adults or slowed development by embryos. Because the thermal effects of dams vary throughout the year, we predict dams impacted late spawners more than early spawners. Similar analyses could shed light on the evolutionary consequences of other environmental perturbations and their interactions. [source] Effect of dietary ,-tocopherol + ascorbic acid, selenium, and iron on oxidative stress in sub-yearling Chinook salmon (Oncorhynchus tshawytscha Walbaum)JOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 1 2009T. L. Welker Summary A three-variable central composite design coupled with surface-response analysis was used to examine the effects of dietary ,-tocopherol + ascorbic acid (TOCAA), selenium (Se), and iron (Fe) on indices of oxidative stress in juvenile spring Chinook salmon. Each dietary factor was tested at five levels for a total of fifteen dietary combinations (diets). Oxidative damage in liver and kidney (lipid peroxidation, protein carbonyls) and erythrocytes (erythrocyte resistance to peroxidative lysis, ERPL) was determined after feeding experimental diets for 16 (early December) and 28 (early March) weeks. Only TOCAA influenced oxidative stress in this study, with most measures of oxidative damage decreasing (liver lipid peroxidation in December and March; ERPL in December; liver protein carbonyl in March) with increasing levels of TOCAA. We also observed a TOCAA-stimulated increase in susceptibility of erythrocytes to peroxidative lysis in March at the highest levels of TOCAA. The data suggest that under most circumstances a progressive decrease in oxidative stress occurs as dietary TOCAA increases, but higher TOCAA concentrations can stimulate oxidative damage in some situations. Higher levels of TOCAA in the diet were required in March than in December to achieve comparable levels of protection against oxidative damage, which may have been due to physiological changes associated with the parr-smolt transformation. Erythrocytes appeared to be more sensitive to variation in dietary levels of TOCAA than liver and kidney tissues. Using the March ERPL assay results as a baseline, a TOCAA level of approximately 350,600 mg/kg diet would provide adequate protection against lipid peroxidation under most circumstances in juvenile Chinook salmon. [source] Non-direct homing behaviours by adult Chinook salmon in a large, multi-stock river systemJOURNAL OF FISH BIOLOGY, Issue 1 2008M. L. Keefer Two non-direct homing behaviours, overshoot of natal tributaries and temporary non-natal tributary use, were evaluated for 5150 radio-tagged spring,summer Chinook salmon Oncorhynchus tshawytscha from 40 populations in the large Columbia River system. Over 7 years, 2,44% (mean = 15%) of individuals within each group temporarily entered presumed non-natal tributaries. In addition, many Chinook salmon from lower river tributaries initially travelled 3 to >250 km upstream in the main-stem river beyond confluences with presumed natal tributaries before returning to the natal sites (,overshoot'). Both overshoot and temporary tributary use behaviours declined exponentially with increasing distance from the natal tributary. Non-direct homing also increased later in the season as water temperatures rose and was associated with hatchery origin in some cases. The behaviours may reflect a mix of active searching for olfactory cues from natal sites, behavioural thermoregulation and orientation challenges in a large-river migration corridor transformed by dams and reservoirs. While anadromous salmonid homing is generally accurate and precise, these results indicate that route finding can be non-direct, potentially increasing energetic costs and harvest risks during migration. [source] Effects of temperature on disease progression and swimming stamina in Ichthyophonus -infected rainbow trout, Oncorhynchus mykiss (Walbaum)JOURNAL OF FISH DISEASES, Issue 10 2009R Kocan Abstract Rainbow trout, Oncorhynchus mykiss, were infected with Ichthyophonus sp. and held at 10 °C, 15 °C and 20 °C for 28 days to monitor mortality and disease progression. Infected fish demonstrated more rapid onset of disease, higher parasite load, more severe host tissue reaction and reduced mean-day-to-death at higher temperature. In a second experiment, Ichthyophonus -infected fish were reared at 15 °C for 16 weeks then subjected to forced swimming at 10 °C, 15 °C and 20 °C. Stamina improved significantly with increased temperature in uninfected fish; however, this was not observed for infected fish. The difference in performance between infected and uninfected fish became significant at 15 °C (P = 0.02) and highly significant at 20 °C (P = 0.005). These results have implications for changes in the ecology of fish diseases in the face of global warming and demonstrate the effects of higher temperature on the progression and severity of ichthyophoniasis as well as on swimming stamina, a critical fitness trait of salmonids. This study helps explain field observations showing the recent emergence of clinical ichthyophoniasis in Yukon River Chinook salmon later in their spawning migration when water temperatures were high, as well as the apparent failure of a substantial percentage of infected fish to successfully reach their natal spawning areas. [source] The effects of water velocity on the Ceratomyxa shasta infectious cycleJOURNAL OF FISH DISEASES, Issue 2 2009S J Bjork Abstract Ceratomyxa shasta is a myxozoan parasite identified as a contributor to salmon mortality in the Klamath River, USA. The parasite has a complex life cycle involving a freshwater polychaete, Manayunkia speciosa and a salmonid. As part of ongoing research on how environmental parameters influence parasite establishment and replication, we designed a laboratory experiment to examine the effect of water flow (velocity) on completion of the C. shasta infectious cycle. The experiment tested the effect of two water velocities, 0.05 and 0.01 m s,1, on survival and infection of M. speciosa as well as transmission to susceptible rainbow trout and comparatively resistant Klamath River Chinook salmon. The faster water velocity facilitated the greatest polychaete densities, but the lowest polychaete infection prevalence. Rainbow trout became infected in all treatments, but at the slower velocity had a shorter mean day to death, indicating a higher infectious dose. Infection was not detected in Chinook salmon even at a dose estimated to be as high as 80 000 actinospores per fish. The higher water velocity resulted in lower C. shasta infection prevalence in M. speciosa and decreased infection severity in fish. Another outcome of our experiment is the description of a system for maintaining and infecting M. speciosa in the laboratory. [source] An immune-complex glomerulonephritis of Chinook salmon, Oncorhynchus tshawytscha (Walbaum)JOURNAL OF FISH DISEASES, Issue 12 2008J S Lumsden Abstract Chinook salmon from New Zealand were shown to have a generalized membranous glomerulonephritis that was most severe in large fish. Marked thickening of the glomerular basement membrane was the most consistent lesion, with the presence of an electron-dense deposit beneath the capillary endothelium. Severely affected glomeruli also had expansion of the mesangium and loss of capillaries, synechiae of the visceral and parietal epithelium and mild fibrosis of Bowman's capsule. Chinook salmon from British Columbia, Canada with bacterial kidney disease caused by Renibacterium salmoninarum had similar histological lesions. They also had thickened glomerular basement membranes that were recognized by rabbit antiserum to rainbow trout immunoglobulin. This was true only when frozen sections of kidney were used and not formalin-fixed tissue. An attempt to experimentally produce a glomerulopathy in rainbow trout by repeated immunization with killed R. salmoninarum was not successful. Case records from the Fish Pathology Laboratory at the University of Guelph over a 10-year period revealed that a range of species were diagnosed with glomerulopathies similar to those seen in Chinook salmon. The majority of these cases were determined to have chronic inflammatory disease. This report has identified the presence of immunoglobulin within thickened basement membranes of Chinook salmon with glomerulonephritis and supports the existence of type III hypersensitivity in fish. [source] Development and physiology of gastric dilation air sacculitis in Chinook salmon, Oncorhynchus tshawytscha (Walbaum)JOURNAL OF FISH DISEASES, Issue 8 2007L G Forgan Abstract The syndrome known as gastric dilation air sacculitis (GDAS) has previously been shown to affect Chinook salmon, Oncorhynchus tshawytscha, in seawater (SW) aquaculture. Feed and osmoregulatory stress have been implicated as potential epidemiological co-factors. The development and physiology of GDAS was investigated in SW and freshwater (FW) adapted smolts. Diet A (low-cohesion pellets) and diet B (high-cohesion pellets) were fed to both FW- and SW-adapted fish. GDAS was induced only in the SW trial on feeding diet A. Stimulated gastro-intestinal (GI) smooth muscle contractility, and fluid transport by the pyloric caeca were different in GDAS-affected fish, which also showed osmoregulatory dysfunction. Cardiac stomach (CS) smooth muscle contractility in response to acetylcholine and potassium chloride (KCl) was significantly reduced in fish fed diet A relative to controls from weeks 3,5. In contrast, maximal pyloric sphincter (PS) circular smooth muscle contraction in response to KCl was significantly elevated in fish fed diet A in weeks 4 and 5. Serum osmolality was elevated in GDAS-affected fish from week 2 of the SW trial. Fluid transport from the mucosal to serosal surface of isolated pyloric caeca was significantly reduced in weeks 3, 4 and 5 in SW fish fed diet A. Gastric evacuation from the stomach of healthy fish was shown to be significantly different when diets of low- and high-cohesion were fed. The results are consistent with the intestinal brake playing a role in the development of the disease. [source] A stochastic modelling approach to describing the dynamics of an experimental furunculosis epidemic in Chinook salmon, Oncorhynchus tshawytscha (Walbaum)JOURNAL OF FISH DISEASES, Issue 2 2007H Ogut Abstract A susceptible-infected-removed (SIR) stochastic model was compared to a susceptible-latent-infectious-removed (SLIR) stochastic model in terms of describing and capturing the variation observed in replicated experimental furunculosis epidemics, caused by Aeromonas salmonicida. The epidemics had been created by releasing a single infectious fish into a group of susceptible fish (n = 43) and progress of the epidemic was observed for 10 days. This process was replicated in 70 independent groups. The two stochastic models were run 5000 times and after every run and every 100 runs, daily mean values of each compartment were compared to the observed data. Both models, the SIR model (R2 = 0.91), and the SLIR model (R2 = 0.90) were successful in predicting the number of fish in each category at each time point in the experimental data. Moreover, between-replicate variability in the stochastic model output was similar to between-replicate variability in the experimental data. Generally, there was little change in the goodness of fit (R2) after 200 runs in the SIR model whereas 500 runs were necessary to have stable predictions with the SLIR model. In the SIR model, on an individual replicate basis, ,80% of 5000 simulated replicates had R2 = 0.7 and above, whereas this ratio was slightly higher (82%) with the SLIR model. In brief, both models were equally effective in predicting the observed data and its variance but the SLIR model was advantageous because it differentiated the latent, i.e. infected but not having the ability to discharge pathogen, from the infectious fish. [source] Pathogens as potential selective agents in the wildMOLECULAR ECOLOGY, Issue 22 2009MÉLANIE DIONNE Pathogens are considered a serious threat to which wild populations must adapt, most particularly under conditions of rapid environmental change. One way host adaptation has been studied is through genetic population structure at the major histocompatibility complex (MHC), a complex of adaptive genes involved in pathogen resistance in vertebrates. However, while associations between specific pathogens and MHC alleles or diversity have been documented from laboratory studies, the interaction between hosts and pathogens in the wild is more complex. As such, identifying selective agents and understanding underlying co-evolutionary mechanisms remains a major challenge. In this issue of Molecular Ecology, Evans & Neff (2009) characterized spatial and temporal variation in the bacterial parasite community infecting Chinook salmon (Oncorhynchus tshawytscha) fry from five populations in British Columbia, Canada. They used a 16S rDNA sequencing-based approach to examine the prevalence of bacterial infection in kidney and looked for associations with MHC class I and II genetic variability. The authors found a high diversity of bacteria infecting fry, albeit at low prevalence. It was reasoned that spatial variability in infection rate and bacterial community phylogenetic similarity found across populations may represent differential pathogen-mediated selection pressures. The study revealed some evidence of heterozygote advantage at MHC class II, but not class I, and preliminary associations between specific MHC alleles and bacterial infections were uncovered. This research adds an interesting perspective to the debate on host,pathogen co-evolutionary mechanisms and emphasizes the importance of considering the complexity of pathogen communities in studies of host local adaptation. [source] Eco-evolutionary vs. habitat contributions to invasion in salmon: experimental evaluation in the wildMOLECULAR ECOLOGY, Issue 1 2008MICHAEL T. KINNISON Abstract Although trait evolution over contemporary timescales is well documented, its influence on ecological dynamics in the wild has received much less attention particularly compared to traditional ecological and environmental factors. For example, evolution over ecologically relevant timescales is expected in populations that colonize new habitats, where it should theoretically enhance fitness, associated vital rates of survival and reproduction, and population growth potential. Nonetheless, success of exotic species is much more commonly attributed to ecological aspects of habitat quality and ,escape from enemies' in the invaded range. Here, we consider contemporary evolution of vital rates in introduced Chinook salmon (Oncorhynchus tshawytscha) that quickly colonized New Zealand and diverged over c. 26 generations. By using experimental translocations, we partitioned the roles of evolution and habitat quality in modifying geographical patterns of vital rates. Variation in habitat quality within the new range had the greatest influence on broad geographical patterns of vital rates, but locally adapted salmon still exhibited more than double the vital rate performance, and hence fitness, of nonlocal counterparts. The scope of this fitness evolution far exceeds the scale of divergence in trait values for these populations, or even the expected fitness effects of particular traits. These results suggest that contemporary evolution can be an important part of the eco-evolutionary dynamics of invasions and highlight the need for studies of the emergent fitness and ecological consequences of such evolution, rather than just changes in trait values. [source] Fine-scale natal homing and localized movement as shaped by sex and spawning habitat in Chinook salmon: insights from spatial autocorrelation analysis of individual genotypesMOLECULAR ECOLOGY, Issue 14 2006H. M. NEVILLE Abstract Natal homing is a hallmark of the life history of salmonid fishes, but the spatial scale of homing within local, naturally reproducing salmon populations is still poorly understood. Accurate homing (paired with restricted movement) should lead to the existence of fine-scale genetic structuring due to the spatial clustering of related individuals on spawning grounds. Thus, we explored the spatial resolution of natal homing using genetic associations among individual Chinook salmon (Oncorhynchus tshawytscha) in an interconnected stream network. We also investigated the relationship between genetic patterns and two factors hypothesized to influence natal homing and localized movements at finer scales in this species, localized patterns in the distribution of spawning gravels and sex. Spatial autocorrelation analyses showed that spawning locations in both sub-basins of our study site were spatially clumped, but the upper sub-basin generally had a larger spatial extent and continuity of redd locations than the lower sub-basin, where the distribution of redds and associated habitat conditions were more patchy. Male genotypes were not autocorrelated at any spatial scale in either sub-basin. Female genotypes showed significant spatial autocorrelation and genetic patterns for females varied in the direction predicted between the two sub-basins, with much stronger autocorrelation in the sub-basin with less continuity in spawning gravels. The patterns observed here support predictions about differential constraints and breeding tactics between the two sexes and the potential for fine-scale habitat structure to influence the precision of natal homing and localized movements of individual Chinook salmon on their breeding grounds. [source] Identifying environmental signals from population abundance data using multivariate time-series analysisOIKOS, Issue 11 2009Masami Fujiwara Individual organisms are affected by various natural and anthropogenic environmental factors throughout their life history. This is reflected in the way population abundance fluctuates. Consequently, observed population dynamics are often produced by the superimposition of multiple environmental signals. This complicates the analysis of population time-series. Here, a multivariate time-series method called maximum autocorrelation factor analysis (MAFA) was used to extract underlying signals from multiple population time series data. The extracted signals were compared with environmental variables that were suspected to affect the populations. Finally, a simple multiple regression analysis was applied to the same data set, and the results from the regression analysis were compared with those from MAFA. The extracted signals with MAFA were strongly associated with the environmental variables, suggesting that they represent environmental factors. On the other hand, with the multiple regression analysis, one of the important signals was not identifiable, revealing the shortcoming of the conventional approach. MAFA summarizes data based on their lag-one autocorrelation. This allows the identification of underlying signals with a small effect size on population abundance during the observation. It also uses multiple time series collected in parallel; this enables us to effectively analyze short time series. In this study, annual spawning adult counts of Chinook salmon at various locations within the Klamath Basin, California, were analyzed. [source] Interspecific Effects of Artifically Propagated Fish: an Additional Conservation Risk for SalmonCONSERVATION BIOLOGY, Issue 6 2002Phillip S. Levin We tested the hypothesis that hatchery-reared steelhead salmon ( Oncorhynchus mykiss) released into the Snake River Basin negatively affect the survival of wild Snake River steelhead and chinook ( O. tshawytscha) salmon. Because climatic conditions can influence salmon survival, we included an index of the El Niño,Southern Oscillation ( ENSO) as a covariate in our analyses. Based on time series of hatchery releases and rates of smolt-to-adult survival, we demonstrate that the survival of wild chinook salmon is negatively associated with hatchery releases of steelhead. The state of the ( ENSO) did not affect the strength of this relationship. We observed no relationship between survival of wild steelhead and steelhead hatchery releases. Our results suggest that industrial-scale production of hatchery fish may hinder the recovery of some threatened salmonids and that the potential interspecific impact of hatcheries must be considered as agencies begin the process of hatchery reform. Resumen: Por más de 120 años, las granjas han liberado números enormes de salmones del Pacífico para compensar las numerosas agresiones humanos a sus poblaciones, sin embargo, los impactos ecológicos de este esfuerzo masivo son poco entendidos. Evaluamos la hipótesis de que la trucha cabeza de acero ( Oncorhynchus mykiss) criada en granjas y liberada en la cuenca del Río Snake afecta negativamente la supervivencia de truchas cabeza de acero y salmones chinook ( O. tshawytscha) silvestres. Puesto que las condiciones climáticas pueden influir sobre la supervivencia del salmón, incluimos un índice de la Oscilación del Niño del Sur como covariable del análisis. En base a series de tiempo de las liberaciones de las granjas y las tasas de supervivencia hasta adulto de peces migrantes al mar, demostramos que la supervivencia del salmón chinook silvestre está negativamente correlacionada con las liberaciones de truchas cabeza de acero de las granjas. El estado de la Oscilación del Niño del Sur no afectó el grado de correlación. No observamos relación alguna entre la supervivencia de las truchas silvestres y las liberaciones de las granjas. Nuestros resultados sugieren que la producción a escala industrial de peces de granja puede obstaculizar la recuperación de algunos salmónidos amenazados y que el impacto interespecífico potencial de las granjas debería ser considerado en cuanto las agencias inicien el proceso de reforma de las granjas. [source] Synergistic effects of esfenvalerate and infectious hematopoietic necrosis virus on juvenile chinook salmon mortalityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005Mark A. Clifford Abstract Sublethal concentrations of pollutants may compromise fish, resulting in increased susceptibility to endemic pathogens. To test this hypothesis, juvenile chinook salmon (Oncorhynchus tshawytscha) were exposed to sublethal levels of esfenvalerate or chlorpyrifos either alone or concurrently with infectious hematopoietic necrosis virus (IHNV). Three trials were performed with fish exposed to concentrations of IHNV between 0.8 × 102 and 2.7 × 106 plaque-forming units/ml and to 5.0 ,g/L of chlorpyrifos or 0.1 ,g/L of esfenvalerate. The presence and concentration of IHNV in dead fish were assayed by virus isolation and plaque assay techniques, respectively. Among groups exposed to both esfenvalerate and IHNV, 83% experienced highly significant (p < 0.001) mortality, ranging from 20 to 90% at 3 d post-virus exposure, and cumulatively died from 2.4 to 7.7 d sooner than fish exposed to IHNV alone. This trend was not seen in any other treatment group. Virus assays of dead fish indicate a lethal synergism of esfenvalerate and IHNV. Chlorpyrifos had no observed effect on total mortality or IHNV susceptibility. The present results suggest that accepted levels of pollutants may be seemingly nonlethal to fish but, in fact, be acting synergistically with endemic pathogens to compromise survivorship of wild fish populations through immunologic or physiologic disruption. [source] EVOLUTION OF TEMPORAL ISOLATION IN THE WILD: GENETIC DIVERGENCE IN TIMING OF MIGRATION AND BREEDING BY INTRODUCED CHINOOK SALMON POPULATIONSEVOLUTION, Issue 4 2000Thomas P. Quinn Abstract. The timing of migration and breeding are key life-history traits; they are not only adaptations of populations to their environments, but can serve to increase reproductive isolation, facilitating further divergence among populations. As part of a study of divergence of chinook salmon, Oncorhynchus tshawytscha, populations, established in New Zealand from a common source in the early 1900s, we tested the hypotheses that the timing of migration and breeding are under genetic control and that the populations genetically differ in these traits despite phenotypic overlap in timing in the wild. Representatives of families from two populations were collected within a day or two of each other, reared in a common environment, and then released to sea from each of two different rivers, while other family representatives were retained in fresh water to maturity. The date of maturation of fish held in fresh water and the dates of return from the ocean and maturation of fish released to sea all showed significant differences between the two populations and among families within populations. The very high heritabilities and genetic correlations estimated for migration and maturation date indicated that these traits would respond rapidly to selection. Combined with the results of related studies on these chinook salmon populations, it appears that spawning time may not only evolve during the initial phases of divergence, but it may play an important role in accelerating divergence in other traits. [source] Migratory costs and contemporary evolution of reproductive allocation in male chinook salmonJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2003M. T. Kinnison Abstract Energetically demanding migrations may impact the resources available for reproductive trait development and activity, and hence favour evolution of new investment strategies for remaining resources. We conducted a large-scale experiment to evaluate the proximate cost of migration on male reproductive investment in chinook salmon (Oncorhynchus tshawytscha) and contemporary evolution of reproductive allocation. Experimentally induced differences in migratory costs (17 km inland and 17 m elevation vs. 100 km and 430 m) influenced dorsal hump size and upper jaw length, two traits influencing male mating success that are developed during migration. Longer migration also reduced tissue energy reserves available for competition and length of breeding life. Corresponding shifts in the balance between natural and sexual selection appear to have been responsible for heritable population divergence in secondary sexual trait investment, in approximately 26 generations, following colonization of spawning sites with different migratory demands. [source] Long-distance downstream movements by homing adult chinook salmonJOURNAL OF FISH BIOLOGY, Issue 3 2006M. L. Keefer Unusually long downstream movements totalling several hundred kilometres to >1100 km were observed during upstream homing migrations of radio-tagged spring chinook salmon Oncorhynchus tshawytscha in the Columbia and Snake Rivers, U.S.A. Downstream migrants, identified by their repeated ascension and fallback over a series of large hydroelectric dams within the migration corridor, were primarily hatchery-origin males. [source] Relationships between metabolic rate, muscle electromyograms and swim performance of adult chinook salmonJOURNAL OF FISH BIOLOGY, Issue 4 2003D. R. Geist Oxygen consumption rates of adult spring chinook salmon Oncorhynchus tshawytscha increased with swim speed and, depending on temperature and fish mass, ranged from 609 mg O2 h,1 at 30 cm s,1 (c. 0·5 BL s,1) to 3347 mg O2 h,1 at 170 cm s,1 (c. 2·3 BL s,1). Corrected for fish mass, these values ranged from 122 to 670 mg O2 kg,1 h,1, and were similar to other Oncorhynchus species. At all temperatures (8, 12·5 and 17° C), maximum oxygen consumption values levelled off and slightly declined with increasing swim speed >170 cm s,1, and a third-order polynomial regression model fitted the data best. The upper critical swim speed (Ucrit) of fish tested at two laboratories averaged 155 cm s,1 (2·1 BL s,1), but Ucrit of fish tested at the Pacific Northwest National Laboratory were significantly higher (mean 165 cm s,1) than those from fish tested at the Columbia River Research Laboratory (mean 140 cm s,1). Swim trials using fish that had electromyogram (EMG) transmitters implanted in them suggested that at a swim speed of c. 135 cm s,1, red muscle EMG pulse rates slowed and white muscle EMG pulse rates increased. Although there was significant variation between individual fish, this swim speed was c. 80% of the Ucrit for the fish used in the EMG trials (mean Ucrit 168·2 cm s,1). Bioenergetic modelling of the upstream migration of adult chinook salmon should consider incorporating an anaerobic fraction of the energy budget when swim speeds are ,80% of the Ucrit. [source] Sporadic neoplasms of farmed chinook salmon, Oncorhynchus tshawytscha (Walbaum), from New ZealandJOURNAL OF FISH DISEASES, Issue 7 2003J S Lumsden Abstract Eight separate neoplasms with five distinct morphologies are described in the present report. The spontaneous neoplasms were identified in farmed chinook salmon, Oncorhynchus tshawytscha (Walbaum), during processing. The masses were examined histologically and were classified as teratoma, rhabdosarcoma, biliary and renal cystadenomas, renal carcinoma and three leiomyomas. This represents one neoplasm detected for every 125 000 fish processed during the sampling period. [source] Ribosomal DNA sequences indicate isolated populations of Ichthyophonus hoferi in geographic sympatry in the north-eastern Pacific OceanJOURNAL OF FISH DISEASES, Issue 10 2002C D Criscione Abstract Infections of Ichthyophonus hoferi, a cosmopolitan parasite of marine fish, have recently been reported in rockfish, Sebastes spp., from the north-eastern Pacific. Because I. hoferi also infects Pacific herring, Clupea pallasi Valenciennes, and salmonids in this region, we wanted to determine if Ichthyophonus parasites from rockfishes, Pacific herring and chinook salmon, Oncorhynchus tshawytscha (Walbaum), were the same. Small subunit ribosomal deoxyribonucleic acid sequence data revealed two haplotypes that were fixed among host species in geographic sympatry, one from rockfish and the other from both Pacific herring and salmon. These isolated populations of Ichthyophonus could be part of the same species that are ecologically separated because of host behaviours, or they could be distinct species that are host specific. Dietary patterns of the hosts indicate that ecological separation among hosts is possible, but the presence of distinct species may better explain the observed Ichthyophonus haplotype association with host species. [source] Gastric dilation and air sacculitis in farmed chinook salmon, Oncorhynchus tshawytscha (Walbaum)JOURNAL OF FISH DISEASES, Issue 3 2002J S Lumsden A syndrome affecting cultured chinook salmon, Oncorhynchus tshawytscha (Walbaum), characterized by distended abdomens, gastric dilation, air sacculitis (GDAS), increased feed conversion rates and increased mortality has been recognized in New Zealand. Affected fish were most obvious in sea cages but were also present in fresh water. Mortality rates associated with this condition were highest in late summer and approached 6% per month. A dilated and flaccid stomach, without visible rugal folds containing copious oil, watery fluid or undigested feed was typical. Gastric mucosal ulceration or inflammation were not present. The air sacculitis consisted of a thickened, dilated bladder with a mixed mucosal inflammatory infiltrate and a luminal exudate associated with large numbers of morphologically diverse bacteria. Gastric dilation or air sacculitis occurred alone or together in the same fish. In a group of 20 subclinically affected fish with or without gastric dilation, there were no significant differences in weight, length, serum osmolality, sodium, total protein or packed cell volume. Twenty-three severely affected fish had significantly (P < 0.05) higher serum osmolality but similar sodium and total protein to that of clinically normal fish. [source] Gill disease of marine fish caused by infection with Neoparamoeba pemaquidensisJOURNAL OF FISH DISEASES, Issue 9 2001B L Munday Amoebic gill disease (AGD) of maricultured salmonids, turbot, Scophthalmus maximus (L.), European seabass, Dicentrarchus labrax (L.), and sharpsnout seabream, Diplodus puntazzo (Cetti), caused by Neoparamoeba pemaquidensis has been reported from Australia (Tasmania), Ireland, France, Chile, North America (Washington State and California) and Spain. Of the salmonids, Atlantic salmon, Salmo salar L., appears to be the most susceptible with rainbow trout, Oncorhynchus mykiss (Walbaum), also suffering significant disease. Only minor outbreaks have been reported in coho, O. kisutch (Walbaum), and chinook salmon, O. tshawytscha (Walbaum). The disease now accounts for 10,20% of production costs of Atlantic salmon in Tasmania and has lead to temporary abandonment of culture of this species in parts of Spain. It is of lesser, but still significant, importance in other countries. Much is known about the pathology of AGD but the pathophysiology of the disease is poorly understood. There is evidence that non-specific immunity is involved in fish acquiring resistance to AGD, but no unequivocal evidence exists for protection as a result of specific immune responses. To date, for salmonids, the only effective treatment for AGD is a freshwater bath. Control procedures based on modification of management strategies have been minimal and virtually unresearched. [source] Conjugation of isometamidium chloride to antibodies and the use of the conjugate against the haemoflagellate, Cryptobia salmositica Katz, 1951: an immuno-chemotherapeutic strategyJOURNAL OF FISH DISEASES, Issue 8 2001B F Ardelli The trypanocidal drug isometamidium chloride (Samorin) was conjugated to polyclonal and monoclonal antibodies produced against the pathogenic haemoflagellate Cryptobia salmositica. Under in vitro conditions the unconjugated drug normally accumulates rapidly in the kinetoplast in the parasite; however, once it was conjugated to antibodies (either polyclonal or monoclonal) it was found throughout the parasite. Isometamidium conjugated to polyclonal antibodies lysed C. salmositica under in vitro conditions, but parasites were not agglutinated. In contrast, isometamidium conjugated to monoclonal antibodies (against a 200 kDa surface membrane glycoprotein) did not lyse C. salmositica, but parasites were agglutinated. Because of the low efficacy of the monoclonal conjugate against the parasite in vitro, its cryptobiocidal effect was not evaluated further. The infectivity of C. salmositica (incubated either in culture medium or whole blood) was reduced in fish after in vitro exposure to isometamidium conjugated to polyclonal antibodies. Parasitaemias were reduced in infected chinook salmon, Oncorhynchus tshawytscha, after treatment with isometamidium conjugated to polyclonal antibodies. [source] Efficacy of manual removal and ivermectin gavage for control of Salmincola californiensis (Wilson) infestation of chinook salmon, Oncorhynchus tshawytscha (Walbaum), captive broodstocksJOURNAL OF FISH DISEASES, Issue 4 2001K A Johnson Captive broodstocks of spring chinook salmon, Oncorhynchus tshawytscha, were initiated from collections of naturally produced parr from the Lemhi River, a tributary of the Salmon River, ID, USA. These fish were subsequently demonstrated to be infested with the copepod parasite Salmincola californiensis. The initial prevalence of visible adult parasites for 4 years of observations made shortly after collection varied from 19.7 to 71.6%. Both the prevalence and intensity of the infestation increased in the freshwater culture of these fish. Manual removal was initiated as a means of control and practiced at monthly intervals. The number of Salmincola removed decreased in the ensuing 5 months, but the prevalence was not greatly affected. Ivermectin (22,23 dihydroavermectin), was diluted with saline and delivered by gavage at the rate of 0.20 mg kg,1 body weight when the groups were being handled for the manual removal of parasites. Either two or three ivermectin treatments were given to four broodstocks of chinook salmon depending on the severity of the infestation and on the extent of gill pathology. The combination of manual removal and ivermectin gavage eliminated live Salmincola and resolved all associated necrosis of the gill tissues. There was no trend to indicate that individual chinook salmon possessed a natural resistance to reinfestation. [source] | ||||||||||||||||||||||||||||